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We experimentally investigate whether crystal polarity affects the growth of GaN nanowires in plasma-assisted molecular beam epitaxy and whether their formation has to be induced by defects. For this purpose, we prepare smooth and coherently strained AlN layers on 6H-SiC(0001) and SiC(0001̅) substrates to ensure a well-defined polarity and an absence of structural and morphological defects. On N-polar AlN, a homogeneous and dense N-polar GaN nanowire array forms, evidencing that GaN nanowires form spontaneously in the absence of defects. On Al-polar AlN, we do not observe the formation of Ga-polar GaN NWs. Instead, sparse N-polar GaN nanowires grow embedded in a Ga-polar GaN layer. These N-polar GaN nanowires are shown to be accidental in that the necessary polarity inversion is induced by the formation of SixN. The present findings thus demonstrate that spontaneously formed GaN …
American Chemical Society
Publication date: 
12 Dec 2012

Sergio Fernández-Garrido, Xiang Kong, Tobias Gotschke, Raffaella Calarco, Lutz Geelhaar, Achim Trampert, Oliver Brandt

Biblio References: 
Volume: 12 Issue: 12 Pages: 6119-6125
Nano letters